202 The American Geologist. October, 1903 
The origin of these sandstone dikes is probably identical 
with the sandstone dikes of California, that is, they are sand 
filled fissures formed during - earthquakes. Nevertheless, as 
they are so irregular both in direction and size, and also con- 
fined apparently to such a small area, it is possible that they 
are the filling of fissures, produced by landslides caused by 
the river undermining its bank. 
THE RICHMOND GROUP IN OHIO AND INDIANA 
AND ITS SUBDIVISIONS, WITH A NOTE 
ON THE GENUS STROPHOMEN A 
AND ITS TYPE. 
By John M. Nicklks, Sparta, 111. 
CONTENTS. 
I . Definition and characterization 202 
II . Subdivisions 205 
1 . The Waynesville or Bythopora meeki beds 205 
2. The Liberty or Strophomena planumbona beds 207 
3 . The Whitewater or Homotrypa wortheni beds 208 
4 . The Madison formation 210 
III. Note on the genus Strophomena and its type 214 
IV. Table showing stratigraphic sequence of subdivisions... 218 
I. Definition and characterization. 
The term Richmond group was first used by Winchell and 
Ulrich, in the Geology of Minnesota, III, Part 2, 1897, p. ciii, 
and defined as follows : 
"Resting on the Lorraine there is a series of alternating thin bedded 
shales and limestones and in some localities finally a sandstone, in all 
quite 350 feet thick in southwestern Ohio and southeastern Indiana. 
Almost the entire series is excellently exposed at Richmond, Indiana, 
so that the name Richmond group which we propose to apply to the 
series is eminently appropriate." 
In a footnote they say : 
"Professor Orton's name Lebanon would have been adopted had his 
name not been used before for a division of the Trenton period by 
professor Safford. The Richmond exposures besides are larger and 
more characteristic of the group than those near Lebanon, Ohio." 
"East and southeast of Oxford in Ohio, the whole group consists of 
thin bedded limestones and shales, but at Richmond the upper part 
shows an increase of arenaceous matter while the uppermost layers of 
shale have become harder and include one or two layers of impure lime- 
stone. Southward from this locality in Ripley and Jefferson counties 
